Luxottica Group, the Italian company that sells Ray Ban and Oakley sunglasses, reported net sales of

Question:

Luxottica Group, the Italian company that sells Ray Ban and Oakley sunglasses, reported net sales of € 7.1 billion in 2012 and € 6.2 billion in 2011. Gross profit increased from € 4.1 billion in 2011 to € 4.7 billion in 2012. Was the increase in gross profit caused by (a) an increase in gross profit per sale, (b) an increase in sales volume, or (c) a combination of (a) and (b)?